1. Field of Invention
This invention relates to fuses and is particularly related to a fuse arrangement which is, due to its novel construction, quick melting and exhibits short arcing time and remarkably improved arc-extinguishing characteristics, and hence affords greater protection for electrical and electronic circuitry when excess current flows through the circuit.
2. The Prior Art
A variety of fuses and fuse arrangements are commonly used to protect different electrical and electronic circuits against damage or desctruction when excessive current, i.e., a current in excess of the rated capacity of the fuse, flows through the circuit. Such fuses, for example, are described in U.S. Pat. No. 1,411,946, issued to M. J. West on Apr. 4, 1922; U.S. Pat. No. 2,441,692, issued to R. H. Earle on May 18, 1948, and U.S. Pat. No. 3,061,700 which was granted to A. J. Fister on Oct. 30, 1962.
The fuse described by West comprises a casing having an opening covered by a hinge closure, terminal contact members closing the ends of the casing and a fusible link which connects the terminal contact members.
Earle describes a fuse unit which comprises two so-called "expulsion" fuses connected in series, with each fuse introducing substantial resistance in the circuit during the flow of electric current, thus reducing the value of "fault currents" below the value it would normally be if only a single fuse was employed.
Fister provides a protector for electric circuits to solve the so-called "pressure generation problem." This is accomplished by subdividing the fusible elements of the fuses into a number of short fusible elements, each disposed in different but contiguous compartments, in series, within the housings of the fuses. As shown in FIGS. 1 and 2, Earle provides passageways 34 between successive compartments to provide escape for the vapors and gasses generated in each compartment when the fuse element therein blows, and the various compartments are filled with sand or anhydrous calcium sulfate which act as "arc-quenching" media.
The fuses described in the aforementioned patents, and the prior art fuses in general, are not entirely satisfactory to meet the stringent demands of some electrical circuitry such as, for example, integrated circuitry, in which the fuse elements are frequently stretched between electrodes which are spaced as narrow as 1 to 2 mm apart. Additionally, the arc-extinguishing time in such circuits must be extremely short to protect them against damage or destruction.
Accordingly, it is an object of this invention to provide an improved fuse unit.
It is a further object of this invention to provide an improved fuse unit which is, due to unique arrangement of its various constituents, particularly useful in integrated electric and electronic circuitry.
It is also an object of this invention to provide a fuse arrangement in which the fuse elements are quick melting and which has a short arcing time and remarkably improved arc-extinguishing characteristics.
The foregoing and other objects and improved features of the novel fuse arrangement of this invention will be more clearly comprehended from the following detailed description of the invention taken in conjunction with the accompanying drawings which form a part of this application.